ReWriting URLS

OK. This is what I have
I have 2 domains www.mydomain.com and www.mydomain.net
Both of them are pointing to the same base-directory using the same
index file. What I want to do is make it so that every request
for www.mydomain.com get rewrote as consulting.mydomain.net

I have the following in my .htaccess file in the base directory

RewriteEngine On
RewriteCond %{HTTP_HOST} ^www\.mydomain\.com
RewriteRule ^/(.*) http://consulting.mydomain.net/$1 [R,L]

However, nothing seems to be happening.
Can this be done.. is it a problem with my regular expression?
or am I missing another directive.

Thanks
~Todd